Semiconductor Package with Embedded Die

ABSTRACT

A semiconductor package having an embedded die and solid vertical interconnections, such as stud bump interconnections, for increased integration in the direction of the z-axis (i.e., in a direction normal to the circuit side of the die). The semiconductor package can include a die mounted in a face-up configuration (similar to a wire bond package) or in a face-down or flip chip configuration.

CLAIM OF DOMESTIC PRIORITY

The present application is a division of U.S. patent application Ser.No. 11/595,638, filed Nov. 10, 2006, which is incorporated herein byreference.

FIELD OF THE INVENTION

The present disclosure relates to semiconductor packing.

BACKGROUND OF THE INVENTION

Electronic products such as mobile phones, computers and variousconsumer products require higher semiconductor functionality andperformance in a limited footprint and minimal thickness and weight atthe lowest cost. This has driven the industry to increase integration onthe individual semiconductor chips.

Conventional chip packing technologies have two inherent limitations:(1) the input/output emerges from only one side of the package (i.e.,either from the top or bottom side of the package), and henceintegration in both directions along the “z-axis” is difficult, and (2)the footprint of the package is either equal to the die size for fan-inconfigurations (e.g., WLCSP) or significantly greater than the die sizefor fan-out configurations.

A recent technique for integrating along the z-axis involvesencapsulating a die on a substrate, drilling holes through theencapsulating layer around the periphery of the die, filling the holeswith a metal to form vertical connections extending from the PC board,and forming a circuitry layer over the encapsulating layer to permitmounting of a component over the die. This technique suffers from atleast the following disadvantages. First, using conventional laserdrilling or other known techniques for forming the holes in theencapsulating layer, the pitch between vertical connections is limitedto about 125 microns. Second, the drilling process typically results inheight variations among the vertical connections, which can producetraces of the circuitry layer that are noncoplanar. Because of thisirregularity, a component mounted on top of the circuitry layer may failto establish sufficient physical and electrical contact with the traces,resulting in a nonfunctioning package. Third, the traces in thecircuitry layer typically are flared or enlarged to capture the upperends of the vertical connections, thereby decreasing the density of thetraces. Fourth, the holes in the encapsulating layer must be platedseveral times in order to form solid vertical interconnections.

Accordingly, there remains room for improvement within the field ofsemiconductor packaging.

SUMMARY OF THE INVENTION

According to one aspect, the present disclosure concerns embodiments ofa semiconductor package employing stud bump interconnections forincreased integration in the direction of the z-axis (i.e., in adirection normal to the circuit side of the die). The semiconductorpackage can include a die mounted in a face-up configuration (similar toa wire bond package) or in a face-down or flip chip configuration.

The semiconductor package includes stud bumps formed on the substratearound the periphery of the die. The package also can include anencapsulating layer of a dielectric material at least partiallyencapsulating the die and the stud bumps and a circuitry layer formedover the encapsulating layer. The stud bumps contact respective tracesor contacts of the circuitry layer, thereby establishing respectiveelectrical connections between the substrate and the circuitry layer.The package can include one or more dies and/or any of various active orpassive components mounted on the circuitry layer and electricallyconnected to the substrate via the stud bumps. The side of the substrateopposite the die can be mounted to a motherboard or other components,allowing for integration of the package in either direction along thez-axis.

Where the semiconductor package includes a die mounted to a substrate ina face-up orientation, the circuit side of the die can include studbumps forming vertical interconnections between the die and respectivetraces of the circuitry layer. The traces also are in contact withrespective substrate-level stud bumps, thereby establishing electricalconnections between the circuit side of the die and the substrate,without the need for wire bonds. Where the semiconductor packageincludes a flip chip die, the circuit side of the die can be mounted tothe substrate in a conventional manner, such as with a plurality ofbumps bonded to pads on the circuit side of the die and the substrate.In the flip chip package, only substrate-level stud bumps need beprovided.

Prior to forming the circuitry layer, the upper surfaces of the studbumps can be planarized so that the contact sites of the circuitry layerare substantially coplanar and therefore can form robust connectionswith bumps or other contacts of the component(s) mounted on thecircuitry layer. Another advantage of employing stud bumps for die-leveland substrate-level interconnections is that a relatively fine pitch canbe achieved. In particular embodiments, the pitch of the substrate-levelstud bumps can be about 80 microns or less, and more desirably about 60microns or less. The pitch of the die-level stud bumps in particularembodiments can be about 50 microns or less, and more desirably about 30microns or less. The pitch of stud bumps enables extreme miniaturizationof the overall package size. In particular embodiments, for example, thepackage can have a horizontal footprint (i.e., a footprint in an x-yplane parallel to the major surfaces of the substrate) that is nogreater than the horizontal footprint of the die plus about 0.5 mm inthe x and y directions, and a height or thickness in the z-direction(excluding the substrate) that is no greater than the height orthickness of the die plus about 0.09 mm.

According to another aspect, the semiconductor package includes a diemounted in a face-up orientation on a support layer, an encapsulatinglayer formed over the die, a circuitry layer formed over theencapsulating layer, a plurality of stud bumps forming verticalinterconnections between the circuit side of the die and the circuitrylayer. The support layer can comprise a removable substrate that isremoved from the die after the package is formed. Alternatively, thesupport layer can comprise a heat spreader that absorbs heat generatedby the die and dissipates the heat to atmosphere or the motherboard onwhich the package is mounted.

In one representative embodiment, a semiconductor package comprises asubstrate having first and second, opposed major surfaces, a die mountedto the first major surface of the substrate, a dielectric layer formedon the first major surface and at least partially encapsulating the die,a patterned metal layer formed over the dielectric layer, and aplurality of stud bumps interconnecting locations on the first majorsurface of the substrate with respective locations on the patternedmetal layer.

In another representative embodiment, a semiconductor package comprisesa substrate having first and second, opposed major surfaces, the firstmajor surface having a plurality of pads. The package further comprisesa die carried by the first major surface of the substrate, anencapsulating layer at least partially encapsulating the die, acircuitry layer formed over the encapsulating layer, and a plurality ofmetal interconnects, each extending between and establishing electricalcontact with the circuitry layer and a respective pad on the first majorsurface of the substrate, wherein the metal interconnects have a pitchof about 80 microns or less.

In another representative embodiment, a semiconductor package comprisesa substrate having first and second, opposed major surfaces, the firstmajor surface having a plurality of pads. The package further comprisesa die having a circuit side and a back side, the die being carried bythe first major surface of the substrate with the back side facing thesubstrate, a plurality of substrate-level metal interconnects extendingfrom the first major surface of the substrate, a plurality of die-levelmetal interconnects extending from the circuit side of the die, and adielectric layer formed over the substrate-level and die-level metalinterconnects. A circuitry layer is formed over the dielectric layer,the circuitry layer comprising a plurality of metal traces, at leastsome of the metal traces electrically connecting die-level metalinterconnects with respective substrate-level metal interconnects.

In still another representative embodiment, a semiconductor packagecomprises a support layer, a die having a circuit side and a back side,the die being carried by support layer with the back side facing thesupport layer, a plurality of stud bumps disposed on the circuit side ofthe die, a dielectric layer formed over the circuit side of the die, anda circuitry layer formed over the dielectric layer and comprising aplurality of traces contacting the stud bumps.

In yet another representative embodiment, a method of making asemiconductor package comprises mounting a die on a surface of asubstrate, forming a plurality of stud bumps on the surface of thesubstrate, forming a dielectric layer of dielectric material over thestud bumps and the die so as to at least partially encapsulate the studbumps and the die, and forming a metal circuitry layer over thedielectric layer such that portions of the circuitry layer contact endsurfaces of the stud bumps, the stud bumps thereby establishingelectrical contact between the substrate and the circuitry layer.

In another representative embodiment, a method of making a semiconductorpackage comprises mounting a die in a face-up orientation on a supportlayer, forming a plurality of stud bumps on a circuit side of the die,forming a dielectric layer over the circuit side of the die, and forminga circuitry layer over the dielectric layer, the circuitry layer havinga plurality of traces contacting the stud bumps.

The foregoing and other objects, features, and advantages of theinvention will become more apparent from the following detaileddescription, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a semiconductor packageincluding a die mounted in a face-up orientation, according to oneembodiment;

FIG. 2 is a schematic top plan view of the semiconductor package shownin FIG. 1;

FIG. 3 is a schematic sectional view of a semiconductor packageincluding a die mounted in a face-down, or flip chip, orientation,according to another embodiment.

FIG. 4 is a schematic sectional view of a semiconductor packagecomprising a die mounted on a removable substrate, according to anotherembodiment;

FIG. 5 is a schematic sectional view of a semiconductor packagecomprising a die mounted on a heat spreader, according to yet anotherembodiment; and

FIG. 6 is a schematic sectional view of a semiconductor package similarto FIG. 5, but having at least one stud bump formed on the heat spreaderfor electrically connecting the heat spreader to a source of groundreference voltage.

DETAILED DESCRIPTION OF THE DRAWINGS

As used herein, the singular forms “a,” “an,” and “the” refer to one ormore than one, unless the context clearly dictates otherwise.

As used herein, the term “includes” means “comprises.” For example, adevice that includes or comprises A and B contains A and B but mayoptionally contain C or other components other than A and B. A devicethat includes or comprises A or B may contain A or B or A and B, andoptionally one or more other components such as C.

According to one aspect, the present disclosure concerns embodiments ofa semiconductor package employing stud bump interconnections forincreased integration in the direction of the z-axis. The semiconductorpackage can include a die mounted in a face-up configuration (similar toa wire bond package) or in a face-down or flip chip configuration.

FIG. 1 shows an exemplary embodiment of semiconductor package 10including at least one die 12 positioned in a face-up configuration on asubstrate 14. The die 12 can comprise a conventional semiconductor diehaving any desired configuration. For example, the die 12 can comprise adynamic random access memory (DRAM), a static random access memory(SRAM), a flash memory, a microprocessor, a digital signal processor(DSP) or an application specific integrated circuit (ASIC). The die 12,the substrate 14, and the overall package 10 can have any polygonalshape. In the illustrative embodiment, the die 12, the substrate 14 andthe package 10 are rectangular in shape, but other polygonal shapes,such as square or hexagonal can also be utilized.

The substrate 14 has a first, or “upper”, major surface 16 and anopposed second, or “lower” major surface 18. The terms “upper” and“lower” are used herein for purposes of description; the package neednot have any particular orientation in use. The substrate 14 of package10 (and the substrates of other embodiments disclosed herein) cancomprise any type of substrate such as, for example, a laminate withplural metal layers, a build-up substrate with plural metal layers, aflexible polyimide tape with plural metal layers, and or a ceramicmultilayer substrate. The second major surface 18 can include aplurality of contacts, or pads, 20. Respective solder balls (not shown)can be reflowed on the pads 20 using conventional techniques to provideinterconnection to the circuitry of, for example, a motherboard (notshown) of a final product, such as a computer. Alternatively, othercomponents can mounted to the second major surface 18 of the substrate,such as another die or multiple dies or any of various active or passivecomponents.

The die 12 has a circuit side 22 and a back side 24 mounted on the firstmajor surface 16 of the substrate 14. An adhesive layer 26 comprisingfor example, die attach epoxy, can be used to secure the back side 24 tothe first major surface 16 of the substrate. An encapsulating layer 28,preferably made of a dielectric material, is formed over the die 12 andthe first major surface 16 of the substrate so as to at least partiallyencapsulate the die 12. As shown in FIG. 1, in the illustratedembodiment, the encapsulating layer 28 completely encapsulates the die12 and covers the area of the first major surface 16 surrounding the die12.

In a conventional package having a die in a face-up orientation, thecircuit side 22 is electrically connected to the substrate with wiresbonded to pads on the die circuit side 22 and respective pads on theupper surface of the substrate. In the illustrated configuration, thedie circuit side 22 can be electrically connected to the substrate 14via a plurality of die-level stud bumps 32 and a plurality ofsubstrate-level stud bumps 34 formed around the periphery of the die 12.A patterned metal layer forming a circuitry layer 30 is formed on top ofthe encapsulating layer 28 and includes metal traces that formelectrical connections between stud bumps 32 and respective stud bumps34 so as to electrically connect the die circuit side 22 to the firstmajor surface 16 of the substrate 14. For example, as shown in FIGS. 1and 2, each substrate-level stud bump 34 can be electrically connectedto a respective die-level stud bump 32 by a respective trace 52. Asshown in FIG. 2, each trace 52 can be electrically connected to acontact 54 by a trace 56 for connection to one or more components (notshown) mounted on the circuitry layer 30.

In alternative embodiments, a combination of wire bonds between the diecircuit side 22 and the substrate 14 and electrical connections betweenstud bumps 32 and stud bumps 34 can be used to electrically connect thedie to the substrate. Although less desirable, in still alternativeembodiments, only wire bonds are used to form electrical connectionsbetween the die and the substrate.

The package 10 can also include substrate-level stud bumps 34 thatfunction to electrically connect locations on the first major surface 16of the substrate 14 to one or more components (not shown) on thecircuitry layer 30. In this regard, the circuitry layer 30 can includecontacts or traces forming electrical connections between stud bumps 34and the circuitry of a component mounted on the circuitry layer. Forexample, as shown in FIG. 2, the circuitry layer 30 can include traces58 in contact with the stud bumps 34. Traces 58 can be electricallyconnected to respective contacts 60 by respective traces 62 in thecircuitry layer 30. One or more additional components can be mounted onthe circuitry layer 30, for example, by reflowing solder balls (notshown) on selected one or more of the contacts 54, 60.

Conventional metal plated vias (not shown) can be provided in thesubstrate 14 to electrically connect pads 20 on the second major surface18 of the substrate 14 with conductive pads 48, 50 on the first majorsurface 16 of the substrate 14.

The package can include one or more dies and/or any of various active orpassive components mounted on the circuitry layer 30. Examples of activeor passive components can include, without limitation, capacitors,microelectromechanical machines (MEMs), nanoelectromechanical machines,bioelectromechanical machines (BioMEMs), sensors, planar capacitors,resistors, planar resistors, inductors, fuel cells, antennas, thin filmbatteries, VCSEL's, and photodiodes. As mentioned above, such componentsalso can be mounted to the second major surface 18 of the substrate,allowing for integration of the package in either direction along thez-axis.

Advantageously, the upper surfaces of the stud bumps 32, 34 can beplanarized during the manufacturing process so that the contact sites ofthe circuitry layer 30 are substantially coplanar and therefore can formrobust connections with bumps or other contacts of the component(s)mounted on the circuitry layer. In addition, the stud bumps 32, 34 canbe easily formed while also providing solid vertical interconnections(without internal cavities or through holes) to ensure robust electricalconnections between the die, substrate and other components mounted onthe package. In contrast, where vertical interconnections are formed byfilling holes in a dielectric layer (as described above in theBackground of this disclosure), the holes must be plated several timesto form solid interconnections, which increases the cost and time ofmanufacturing process.

As can be appreciated, the disclosed package allows for unlimitedintegration in the direction of the z-axis on either side of thepackage. The size of the horizontal footprint in the x and y directionscan be adjusted to any desired size based on the input/output density ofthe die, using a combination of fan-in and fan-out routing.

Each of the stud bumps 32 in the illustrated embodiment has an enlargedbase portion 36 and a relatively narrow upper stem portion 38 with thebase portion 36 being affixed to a conductive pad (not shown) on the diecircuit side 22 and the stem portion contacting a conductive trace ofthe circuitry layer 30. The stem portion 38 of each stud bump 32desirably has a transverse planar top surface 40 that contacts a trace52 of the circuitry layer 30. Similarly, each of the stud bumps 34 inthe illustrated embodiment has an enlarged base portion 42 and arelatively narrow upper stem portion 44 with the base portion 42 beingaffixed to a conductive pad 48 on the first major surface 16 of thesubstrate and the stem portion 44 contacting a conductive trace orcontact of the circuitry layer 30. The stem portion 44 of each stud bump34 desirably has a transverse planar top surface 46 that contacts atrace of the circuitry layer 30 (e.g., a trace 52 or 58). Theencapsulating layer 28 and the stud bumps 32, 34 can be planarized usingconventional techniques prior to forming the circuitry layer to form theplanar top surfaces 40, 46 of the stud bumps, as further describedbelow. In other embodiments, the stud bumps 32, 34 can have variousother shapes or configurations.

As shown, the stem portion of each stud bump 32, 34 in particularembodiments, has a transverse cross-sectional profile (taken along anx-y plane parallel to the sides 22, 24 of the die) that is less thanthat of the respective base portion. The stem portion of each stud bump32, 34 in the illustrated embodiment is shown as having a generallycylindrical cross-sectional profile. Alternatively, the stem portion ofeach stud bump 32, 34 can be formed as a truncated cone that tapersslightly from the base portion to the top surface of the stem portion,as disclosed in U.S. Pat. No. 6,940,178, which is incorporated herein byreference. The diameters of the stem portions 38, 44 at the uppersurfaces 40, 46 can be made the same as or slightly smaller than thewidth of the traces in the circuitry layer 30 contacting the stemportions. Advantageously, the traces need not be enlarged or flared tocapture the upper surfaces 40, 46 of the stem portions 38, 44, ascompared to known embedded chip packages where the traces are flared tocapture the upper surfaces of the vertical interconnects. Consequently,the circuitry layer 30 can have a greater density of traces than knownembedded chip packages.

The stud bumps 32, 34 can be made of any suitable metal, such as, forexample, nickel, copper, gold, alloys thereof, or a solder. In someembodiments, the stem portion can be made of a material that is softerthan that of the base portion (as disclosed in U.S. Pat. No. 6,940,178)to promote bonding of the stem portion with a pad brought in contactwith the stem portion.

A significant advantage of employing stud bumps 32, 34 for die-level andsubstrate-level interconnections is that a relatively fine pitch can beachieved. In particular embodiments, the pitch of stud bumps 34 can beabout 80 microns or less, and more desirably about 60 microns or less.The pitch of stud bumps 32 in particular embodiments can be about 50microns or less, and more desirably about 30 microns or less. The pitchof stud bumps enables extreme miniaturization of the overall packagesize. In particular embodiments, for example, the package can have ahorizontal footprint (i.e., a footprint in an x-y plane parallel to thesurfaces 16, 18 of the substrate) that is no greater than the horizontalfootprint of the die plus about 0.5 mm in the x and y directions, and aheight or thickness h₁ (FIG. 1) in the z-direction (excluding thesubstrate) that is no greater than the height or thickness h₂ of the dieplus about 0.09 mm.

The package 10 can be formed as follows. First, the die 12 is attachedto the first major surface 16 of the substrate 14 in a face-uporientation with the circuit side 22 of the die facing away from thesubstrate, as in a conventional wire bond package. The stud bumps 32, 34are then formed on the die circuit side 22 and on the first majorsurface 16 of the substrate around the periphery of the die. Thedielectric layer 28 is formed over the stud bumps 32, 34 and the die 12using conventional techniques, such as by lamination, printing, orspin-on methods. The dielectric layer 28 and the stem portions 38, 44 ofthe stud bumps 32, 34 can then be planarized. Planarizing can beperformed by using conventional chemical mechanical polishing techniquesand/or a mechanical planarization apparatus, such as a grinder.Following the planarization step, the circuitry layer 30 can be formedover the dielectric layer 28 using conventional lithography.

A stud bump 32, 34 can conveniently be formed by an adaptation of a wirebonding process using a wire bonding tool. Particularly, a wire bondingtool configured for forming a wire bond (e.g., a gold or gold alloy wirebond) having a specified wire diameter is employed to form a roughlyspherical (globular) wire end, which is contacted with the surface of aconductive contact site of the substrate or die under conditions offorce and temperature that promote bonding of the globular wire end ontothe conductive line surface, and resulting in some degree of flatteningof the globular wire end. This somewhat flattened globular wire endcomprises a base portion 36, 42 of the bump. Thereafter, the wirebonding tool is pulled away at a specified rate to form a tail, asdescribed for example in U.S. Pat. No. 5,874,780, which is incorporatedherein by reference. Then the tail is trimmed, resulting in a stemportion 38, 44 of the bump.

FIG. 3 shows an exemplary embodiment of another semiconductor package,indicated at 100. The package 100 is similar in construction to thepackage 10 of FIG. 1, although the package 100 has a flip-chipconfiguration. The package 100 in the illustrated embodiment includes asubstrate 102 having opposed, first and second major surfaces 104, 106,respectively, and a die 108 mounted face-down on the first major surface104 of the substrate 102. The die 108 has a circuit side 110 facing thesubstrate 102 and a back side 112 facing away from the substrate 102.

The die 108 can be mounted to the substrate 102 in a conventionalmanner. For example, the interconnection of the circuitry in the die 108can be made by way of bumps 114, which are bonded to an array ofinterconnect pads (not shown) on the die circuit side 110 and to anarray of interconnect pads 116 on the substrate 102. A layer 134 ofepoxy can be formed between the die and the substrate. The second majorsurface 106 of the substrate 102 can include a plurality of contacts, orpads, 118. Respective solder balls (not shown) can be reflowed on thepads 118 using conventional techniques to provide interconnection to thecircuitry of, for example, one or more dies, a motherboard, or any ofvarious other active or passive components.

The package 100 desirably includes a plurality of stud bumps 122, whichcan be formed in the same manner as stud bumps 34 shown in FIG. 1. Asshown in FIG. 3, the stud bumps 122 can be spaced around the peripheryof the die 108 and can be bonded to an array of interconnect pads 124 onthe substrate 102. An encapsulating layer 120, preferably made of adielectric material, is formed over the first major surface 104 of thesubstrate 102 so as to at least partially encapsulate the die 108 andthe stud bumps 122. As shown in FIG. 3, in the illustrated embodiment,the encapsulating layer 120 completely covers the die 108 and the studbumps 122 except for the upper surfaces of the stud bumps.

A patterned metal layer forming a circuitry layer 126 can be formed ontop of the encapsulating layer 120. The circuitry layer 126 includesmetal traces, such as traces 128, that contact the upper surfaces 130 ofstud bumps 122. In this manner, the stud bumps 122 function toelectrically connect the interconnect pads 124 on the first majorsurface 104 of the substrate 102 to one or more components (not shown)mounted on the circuitry layer 126. One or more dies and/or any ofvarious other active or passive components can be mounted on thecircuitry layer 126, thereby allowing for integration of the package ineither direction along the z-axis.

The package 100 can be formed by mounting the die 108 to the substrate102 using conventional techniques and then selectively forming the studbumps 122 on pads 124 on the substrate in the manner described above.Thereafter, the encapsulating layer 120 can be formed over the studbumps 122 and the die using conventional techniques. The upper surfacesof the stud bumps 122 and the encapsulating layer can then be planarizedusing known techniques as described above, after which the circuitrylayer 126 can be formed over the planarized stud bumps and encapsulatinglayer.

FIG. 4 illustrates a semiconductor package 200, according to anotherembodiment. The package 200 includes a die 202 having a circuit side 204and a back side 206. The die 202 is mounted face-up with respect to asupport layer 208; that is, the back side 206 of the die is attached tothe support layer 208, such as by a suitable adhesive layer 210. Inparticular embodiments, the support layer 208 comprises a removablesubstrate 208 that supports the components of the package as it isformed. The removable substrate 208 can be made of any of varioussuitable materials, including, without limitation, a polished siliconwafer, metal (e.g., stainless steel, nickel, or copper), glass, or anyof various suitable polymers (e.g., Teflon or an adhesive material, suchas epoxy).

Stud bumps 212 can be formed on respective interconnect pads (not shown)on the die circuit side 204. An encapsulating layer 214 can be formedover the die 202 and the stud bumps 212. The stud bumps 212 and theencapsulating layer 214 can be planarized, as previously described. Apatterned metal layer 216 can be formed over the encapsulating layer 214and can have traces contacting the upper surfaces 218 of the stud bumps212 and the interconnect pads of any components (not shown) mounted onthe metal layer 216. As shown in FIG. 4, the support layer 208 can havea footprint that extends beyond the edges of the die 202 (in the xand/or y directions) to support portions of the circuitry layer 216 thatextend beyond the edges of the die 202. In alternative embodiments, thesupport layer 208 and the circuitry layer 216 can have a footprint inthe x and y directions that is approximately equal to the footprint ofthe die 202.

After the metal layer 216 is formed, the substrate 208 can be removed,such as by etching away the substrate or peeling it off of the die 202.In a specific example, the removable substrate 208 can be made of a heatsensitive adhesive that can be peeled or otherwise removed from the dieby applying heat to the substrate. If the substrate 208 is peeled off orotherwise removed intact, it can be re-used to form anothersemiconductor package. In other applications, the substrate 208 is notremoved and instead is retained as part of the finished package 200.

In another embodiment, as shown in FIG. 5, the semiconductor package 200can include a heat spreader, or heat sink, 230 rather than a removablesubstrate attached to the back side 206 of the die 202. The heatspreader 230 absorbs heat generated by the die 202 and dissipates theheat to atmosphere or the motherboard on which the package is mounted.The heat spreader 230 can comprise any of various suitable materialsexhibiting good thermal conductivity, such as, for example, silicon,metals (e.g., aluminum, copper, nickel-plated copper, copper/tungsten).The heat spreader 230 in exemplary embodiments can comprise laminatedlayers of different metals, such as two layers of copper sandwiching anintermediate layer of invar or molybdenum. The adhesive layer 210 cancomprise a thermally conductive material to facilitate heat transferfrom the die to the heat spreader 230.

In particular embodiments, the heat spreader 230 also can be coupled toa source (not shown) of ground reference voltage, to thereby allow theheat spreader to function as a ground reference plane. For example, asshown in FIG. 6, the heat spreader 230 can be electrically connected toa source of ground reference voltage via at least one stud bump 232disposed on the heat spreader. As shown, one side of the heat spreadercan be extended past the edge of the die to accommodate the stud bump232. The stud bump 232 can be formed on a contact 234 on the heatspreader 230 and then encapsulated by layer 214. The upper surface ofthe stud bump 232 can be planarized along with stud bumps 212 prior toforming metal layer 216 over the stud bumps 212, 232.

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. I thereforeclaim as my invention all that comes within the scope and spirit ofthese claims.

1. A method of making a semiconductor device, comprising: providing asubstrate; mounting a semiconductor die over a first surface of thesubstrate; forming a plurality of first stud bumps over the firstsurface of the substrate, the first stud bumps including a base portionand a stem portion extending from the base portion; forming a pluralityof second stud bumps over the semiconductor die, the second stud bumpsincluding a base portion and a stem portion extending from the baseportion; and depositing an encapsulant over the substrate, semiconductordie, first stud bumps, and second stud bumps.
 2. The method of claim 1,wherein forming the plurality of first stud bumps includes: providing abond wire; rounding an end of the bond wire to form the base portion;and trimming the bond wire to form the stem portion.
 3. The method ofclaim 1, further including planarizing the encapsulant and the stemportion of the first stud bumps.
 4. The method of claim 1, furtherincluding forming a conductive layer over the encapsulant andelectrically connected to the first stud bumps and second stud bumps. 5.The method of claim 1, further including forming a conductive layer overthe first surface of the substrate prior to forming the first studbumps.
 6. The method of claim 1, further including forming a conductivelayer over a second surface of the substrate opposite the first surfaceof the substrate.
 7. A method of making a semiconductor device,comprising: providing a substrate; mounting a semiconductor die over afirst surface of the substrate; forming a first conductive layer overthe first surface of the substrate; forming a first stud bump over thefirst conductive layer, the first stud bump including a base portion anda stem portion extending from the base portion; and depositing anencapsulant over the substrate, semiconductor die, and first stud bump.8. The method of claim 7, wherein forming the first stud bump includes:providing a bond wire; rounding an end of the bond wire to form the baseportion; and trimming the bond wire to form the stem portion.
 9. Themethod of claim 7, further including planarizing the encapsulant and thestem portion of the first stud bump.
 10. The method of claim 7, furtherincluding forming a second stud bump over the semiconductor die, thesecond stud bump including a base portion and a stem portion extendingfrom the base portion.
 11. The method of claim 7, further includingforming a second conductive layer over the encapsulant and electricallyconnected to the first stud bump.
 12. The method of claim 7, furtherincluding forming a second conductive layer over a second surface of thesubstrate opposite the first surface of the substrate.
 13. The method ofclaim 7, further including forming a heat sink over a second surface ofthe substrate opposite the first surface of the substrate.
 14. A methodof making a semiconductor device, comprising: providing a substrate;mounting a semiconductor die over a first surface of the substrate;forming a first stud bump over the semiconductor die, the second studbump including a base portion and a stem portion extending from the baseportion; and depositing an encapsulant over the substrate, semiconductordie, and first stud bump.
 15. The method of claim 14, wherein formingthe first stud bump includes: providing a bond wire; rounding an end ofthe bond wire to form the base portion; and trimming the bond wire toform the stem portion.
 16. The method of claim 14, further includingplanarizing the encapsulant and the stem portion of the first stud bump.17. The method of claim 14, further including forming a second stud bumpover the first surface of the substrate, the second stud bump includinga base portion and a stem portion extending from the base portion. 18.The method of claim 17, further including forming a conductive layerover the first surface of the substrate prior to forming the second studbump.
 19. The method of claim 14, further including forming a conductivelayer over the encapsulant and electrically connected to the first studbump.
 20. The method of claim 14, further including forming a heat sinkover a second surface of the substrate opposite the first surface of thesubstrate.
 21. A method of making a semiconductor device, comprising:providing a substrate; mounting a semiconductor die over a first surfaceof the substrate; forming a first stud bump over the first surface ofthe substrate, the first stud bump including a base portion and a stemportion extending from the base portion; and depositing an encapsulantover the substrate, semiconductor die, and first stud bump.
 22. Themethod of claim 21, wherein forming the first stud bump includes:providing a bond wire; rounding an end of the bond wire to form the baseportion; and trimming the bond wire to form the stem portion.
 23. Themethod of claim 21, further including forming a second stud bump overthe semiconductor die, the second stud bump including a base portion anda stem portion extending from the base portion.
 24. The method of claim21, further including forming a conductive layer over the encapsulantand electrically connected to the first stud bump.
 25. The method ofclaim 21, further including forming a conductive layer over the firstsurface of the substrate prior to forming the first stud bump.